Trajectory vs charges

[ZVP]

After 2 1/2 years shooting Black Powder I am still confused with the preformance of the POI of the Ball and the relationship to how much powder was loaded!
This weekend I shot my '58 Remington SHeriff's model with 30, 35, 28, and 22 grains of Pyrodex. I was shooting at a7 yard target and untill I tried the 22 Gr load, things were making sense then I loaded the 22 gr load and it all fell apart!
The higher load flattened the POI and the sight picture, the 35gr powder load struck dead-on and the 30 and 28gr caused the ball to strike higher but the 22 gr load shot POI dead-on again!!!
Same Balls, filler and patch and both the 35 gr and the 22gr strike at the same place? Dead-on where it's aimed?
Granted 21 feet isn't much distance to have a trajectory but there was actually about a 2" rise to the Ball but at the lowest load, it went back to centered? HOW???
I was shooting over a rest to ensure the most accurate shot placement for the tests. I was suprised to have a 2" rise between the 35 Gr and the 28 Gr load because 3" would translate to a huge difference at 20 yards!
Did I maybe do something wrong?
I need to re-try this test again.
BTW there was no difference in centering of the ball on paper as all 4 combinations were centered.
Ideas?
ZVP

 

[kwhi43]

In the real world of shooting offhand with just one hand holding the pistol,
you won't see any difference even at 50 yds. The reason you are shooting
high with more powder is the recoil off the rest. It's the way the barrel is
reacting under recoil to whats it is being rested on. In my 44's I can load 18
to 40 grains and I can tell no difference at 50 yds.

 

[B.L.E.]

With revolvers, barrel rise during recoil makes the bullet impact higher than where the barrel is aimed. Heavy bullets usually impact higher than light bullets even though they go slower, because there is more barrel jump with a heavy bullet.

 

[trap4570]

I would try the same test at 25 yards and see what the results are. Seven yards is to short for trajectory tests. I think 25 will allow for a better idea of recoil and barrel time of the ball.